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Siltstone has very few uses. It is rarely the target of mining for use as a construction material or manufacturing feedstock. The intergranular pore spaces in siltstone are too small for it to serve as a good aquifer. It is rarely porous enough or extensive enough to serve as an oil or gas reservoir. Its…

Siltstone can be difficult to identify in the field without close examination. Weathered surfaces often appear to show sedimentary structures where none are present. Different layers weather at different rates. Siltstone is often interbedded with other lithologies. Identification requires breaking off a small piece and observing the grain size. Scraping the surface with a nail…

Siltstone occurs in a wide range of colors. It is usually gray, brown, or reddish brown. White, yellow, green, red, purple, orange, black, and other colors occur. The color is caused by the composition of the grains, the composition of the cement that binds them together, and stains produced by contact with subsurface waters.

The word “silt” does not refer to a specific substance. Instead, it is a word used for loose granular particles in a specific size range. Silt-sized particles range between 0.00015 and 0.0025 inches in diameter, or between 0.0039 and 0.063 millimeters in diameter. They are intermediate in size between coarse clay on the small side…

Siltstone is a sedimentary rock composed mainly of silt-sized particles. It forms where water, wind, or ice deposit silt, and the silt is then compacted and cemented into a rock. Silt accumulates in sedimentary basins throughout the world. It represents a level of current, wave, or wind energy between where sand and mud accumulate. These include fluvial, aeolian, tidal,…